Advanced Materials Research Vol. 1016

Abstract: Predictions are reported for three-dimensional laminar mixed convective heat transfer using nanofluids in a horizontal rectangular duct. Five different types of nanoparticle, Ag, Al₂O_3, Au, Cu and SiO₂ with nanoparticles volume fractions range of 2% to 10% are investigated. In this study, the effects of nanofluids type, nanoparticles volume fraction of nanofluids and the effect of aspect ratio on the thermal fields were examined. Results reveal that the addition of nanoparticles to the base fluid and their volume fraction tend to increase the Nusselt number along the horizontal rectangular duct (i.e., increases the rate of heat transfer). It was also found that the Nusselt number increases as the aspect ratio decreases.

Abstract: Gas turbine is a type of rotary engine that consists of compressor, combustion chamber, and turbine sections. This type of engine works in the Brayton Cycle principle that is compression of atmospheric flow, combustion of air-fuel mixture and expanding high temperature combustion flow to generate power output from turbine. The aim of this study is to determine the duct geometry and flow conditions of the gas turbine blades having the internal cooling ducts that acquire highest heat transfer on turbine blades. For different design of internal duct geometries and flow conditions, Fluent solver is used and solutions are validated with Han’s experimental results.

Abstract: Heating water using solar energy can significantly reduce fossil fuel consumption. However, during the lack of sunlight it is necessary an alternative energy source to supplement or substitute the solar energy. To provide this additional energy, electrical resistances are among the most common devices used. In this work it is presented an experimental analysis of an alternative system to support solar water heating with a better cost-benefit ratio than that of the electrical resistance. For this purpose, a heat pump was designed, constructed and experimentally evaluated as supplementary heating source. To improve the system’s performance, a static evaporator was used as a substitute for the conventional evaporator. The mean coefficient of performance (COP) for the heat pump was 2.15. The same tests were performed utilizing an electrical resistance as heating source and the results obtained in this case were compared with the results obtained using the heat pump. The moderate cost of acquisition and installation of the heat pump allowed an investment return between 2.5 and 3.6 years, depending on the city in which the system is installed. Considering that the equipment has an estimated lifespan of 15 years, the internal rate of return varies from 24.5 to 37.9%, which is attractive for investment.

Abstract: A numerical analysis of thermal phenomena occurring during lined-pipe welding is presented in this paper. Numerical models of surfaces and volumetric heat sources were used to predict the time evolution of the temperature field both in a corrosion-resistance-alloy (CRA) liner, made of SUS304 stainless steel (SS), and for the single-pass girth welding of a carbon-manganese (C-Mn) steel pipe. Using the finite-element code ABAQUS, three-dimensional non-liner heat-transfer analyses was carried out to simulate the gas-tungsten-arc (GTA) welding process used in liner welding and the metal-inert-gas (MIG) welding process consumed in C-Mn steel backing welding. FORTRAN user subroutines were coded to implement the movable welding heat source and heat transfer coefficient models. The thermal history was numerically computed at locations where circumferential angles from the welding start/atop position are 90°, 180° and 270° with respect to axial distances from the weld centerline (WC). Keywords: Finite element analysis FEA, CRA Liner, C-Mn steel backing, Heat source, Thermal history.

Abstract: A computing method of heat transfer in heterogeneous structures is proposed in the paper. The problem is mathematically described as the parabolic boundary value problem with discontinuous coefficients. The generalized solution of this parabolic problem can be approached by the solution of the parabolic boundary problem with smoothed coefficients. To obtain estimates of the solution of the problem with smoothed coefficients the method of numerical solution of stochastic differential equations (SDE) is applied. Some numerical results for honeycomb structures are presented.

Abstract: A numerical study of the effectiveness of phase change material (PCM) used on FORMOSAT-7 at the preliminary design phase is presented in this study. N-eicosane is used as the PCM for its melting temperature. To compare the performance of PCM, different messes of PCM are applied for high-power-dissipating component with short-duty-cycle. The results show that PCM can improve the thermal stability of component by not only moderating peak temperature for worst hot case but also preventing sudden temperature decrease when the power mode of component changed. However, mass addition of PCM reduces the duration of the maximum temperature and the minimum temperature due to the better thermal conductivity of solid phase. Therefore, an optimization of mass is suggested for the application of PCM.

Abstract: In this study, the entropy generation due to the flow of a gravity-driven laminar viscous incompressible fluid through an incline channel is investigated. Fully developed flow field is solved for a Newtonian fluid. Then, the temperature field is numerically resolved using Differential Quadrature Method (DQM) subject to isothermal boundary conditions on the walls and constant rectangular profile at the inlet. The result of DQM is compared to analytical solution and method of lines (MOL) numerical method. Rate of entropy generation is found and its relation with temperature and velocity field is examined.

Abstract: This paper outlines the evaluation of the influence of different empirical correlations to compute air-side heat transfer coefficient on the behavior of a wire-on-tube condenser by performing numerical simulations. A fully predictive simulation model based on first-principles equations and empirical correlations for heat transfer and friction factor is considered. Two-phase flow is modeled using homogeneous model and a void fraction correlation available in the literature is considered. Results show that for the correlations tested, different estimations of heat rate rejected to the environment can be obtained and hence, different thermal hydraulic behavior of the condenser can be obtained. This influence is critical, especially when the global numerical simulation of a domestic refrigerator is considered.

Abstract: Retracted paper: In this paper, the basic principles of HMM, HMM studied three major issues need to be addressed as well as overflow problems in the practical application of how to solve the HMM. Because artificial neural network (ANN) with anti-noise, adaptive, learning ability, recognition speed, etc., taking into account the characteristics of the common features of speech recognition and pattern recognition and artificial neural networks have, this article will get a mixed combination of HMM in ANN model, using ANN to make up for some deficiencies of HMM. Experiments show that the hybrid model recognition rate than the HMM model increased by 4%, but the algorithm still has many defects to be resolved.

Abstract: This paper describes particular pain events to be located as in infant face images with feature extraction algorithm. Nonlinear Fuzzy Robust PCA (NFRPCA) feature extraction is implemented to test its effectiveness in recognizing pain in images. In this work, two classifiers, Fuzzy k-nearest neighbors (Fuzzy k-NN) and k-nearest neighbors (k-NN) are employed. Result shows that the NFRPCA and classifier (Fuzzy k-NN and k-NN) can be used for the recognition of infant pain images with the best accuracy of 89.77%.